Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to an apparatus and process
for extracting oil or bitumen from mineral particles such as
sand.
There are contained in a number of countries in the
world, such as Canada, large deposits of tar ~ands which are
located at or near the surface and are therefore susceptible
to open pit mining for the recovery of bit~nen from the sand,
providing an economical method can be developed for separating
the bitumen from the sand. The term "tar sand" as used herein
will be understood to include biturnen containing sand, which
is also sometimes referred to as "oil sand".
In the northern section of khe Province of Alberta,
Canada, there is located an extraordinarily large deposit
of tar sand of which a substantial portion is located at
or near the surface and it is therefore susceptible to open
pit mining. The bitumen is often present in a ratio of
approximately 15 parts of bitumen to 85 parts of sand by
weight. There is also a small amount of water, clay, silt, and
light viscosity oil present. Accordingly, any process which is
to be devised for separatiny the bitumen from the sand must be
concerned wi~h the handling of vast quantltites of sand in
order to recover a sufficient volume of bitumen to be
comrnercially viable. The process must also avoid polluting
large quantities of water with clav which can be difficult
to separate ~rom the water.
In the Eollowiny speci~ication, "sand" means siliceous
material which is yenerally in a size ranye of 38 to 500 microns
and rnoskly larger than 45 microns; smaller sand particles
(i.e. silt~, and cla~ particles being collectively referred to
as "~ines".
; In connection with one of the existing methods for
extracting bitumen from sand deposits in Northern Alberta,
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after the overburden soil is removed from the tar sand
deposit, the tar sands are remoyed from their in situ
location by means of giant bucket wheel excavators or drag
lines which deposit the tar and sand mixture onto conveyor
belts. These belts transport it to a central processing plant
which can be several miles away, and this distance of course
increases continuously as the source of raw material becomes
further removed from the central processing plant. In exist-
ing installations the tar sand mixture is processed at the
central plant where the bitumen is removed from the sand
by means of a hot water extraction process. The extracted
bitumen is then further processed to remove clay particles,
trace metals and the like and is then processed by conventional
refinery techniques into synthetic crude oil which is capable
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of being transported by pipeline to a central oil refinery
for further processing.
The conventional method of processing the tar sands
... .
involves large amounts of energy to raise the temperature
level of the tar sand and water mixture to a processing temp-
erature of approximately 190F. This is particularly a prob-
lem during the winter months in northern Alberta when the
ambient outside temperature sometimes falls to -60F. In
the hot water -process the large amount of heat required to
-~ raise the temperature of the water makes it uneconomical
to use the ideal amounts of water which results in less
khan optimum quantities of bitumen or tar being recovered
' rom the sand.
The preaently used proceas also involvea enviro-
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mental problems in disposing of the waste products. Desirably,
the sand and clay which are the waste products should be
returned to their original location, but this would involve
transporting a sand and water slurry several rniles, which
would be uneconomical even if this were the only problem. The
presence of clay in the mixture compounds the waste disposal
problem, even if only small amounts of the clay are present. ,~
This is because the clay includes a component, montmorillonite,
which, in the alkali water used in the process, in effect swells
up and forms a thixotropic gel~ The water used in the process,
containing the clay and sand, is dumped into large reser-
voirs, which may be more than 2 square miles in area. Although
these reservoirs are referred to as "settling ponds", in
fact little settling of the clay occurs in any reasonable
space of time, which means that little water can be re-cycled.
The remainder stays in the reservoir, mixed with the clay
gel; eventually the use of this process will result in a
~- series of polluted lakes across the countryside. It will
be understood that this water, due to the content of
alkali and clay, cannot be merely returned to the river from
; which it came.
Another known process for recovery of the tar sand
oil is the so-called "cold water" process, wherein a much
lower (room) temperature water is used with solvents which
will dilute the bitumen so as to cause its separation from
the sand. Thi.s process uses :Less energy, but requires large
amounts of ~olvents and is therefore expensive. ~gain, problems
exist in disposing of the waste water which has substantial
solvents and which contains suspended clay.
Many patents have issued concerning variations of
these extraction me-thods; one prior patent which gives an
ex~ensive review of the art is U.50 Patent 3,605,975 ~o Brimhall.
The present invention provides a process ~hich can
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be operated ~ith "cold'l water (i.e. ~ater which only needs
heating in winter months~; which can ~e operated w~th addltion
of little or no solvents; and ~ich can be operated with
neutral pH water so that the clay in the tar sands does not
form a gel and can be removed, to a large extent, in a settling
tank.
Both the hot and cold water process, in effect,
cause a softening or disolving of the bitumen to cause this
to be released from the sand particles. I have found that
10 it is possible to cause the bitumen to be substantially
entirely separated from the sand particles (excepting ~ines)
by a mechanism which is wholly or very largely mechanical,
and which can operate successfully in the a~sence of any
alkali, and in the absencé of heating above that required to
bring the water, in which a slurry of the tar sands i5 formed,
up to normal room temperatures. The substantially entire
separation produced in accordance with this invention allows
virtually clean sand to be separated from a first phase product
~-~ which contains bitumen and fines, this product being then
20 subject to further processing. The process of my invention
is essentially an abrading and controlled separation process
wherein a slurry of the tar sands mixed with a small amount of
water is firstly produced by a milling process ~7hich breaks
away bit~nen from the sand, the slurry then being suhjected
to an agitation or shearing action which causes further
separation of bitumen from sand, and then being moved hor-
izontally at a controlled speed over a static clean bed of
sand which is sand which has settled -from the pulp after
releasing its bitumen. The process includes a water dilution
stage which precedes the last stage. The unique manner in
which the diluted slurry or pulp is caused to flow over the
sand bed ensures that any bitumen coated particles which
reach the sand hed are rolled and abraded along ~he sand bed
, . . . .
37
in such a way as to release the bitumen and to allow this to
float to the top of the water. The process is self-regulating
in the sense that the movement imparted to the pulp is
sufficient to maintain any bitumen coated sand particles
(and of course any bitumen lumps) in movement over the sand
bed, the speed of the pulp being however sufficiently slow
that bitumen free sand particles ~other than fines) can
settle on the bed. Accordingly, the sand bed only recei~es
clean particles.
; 10 At the temperatures at which my process is normally
operated, bitumen is slightly heavier than water, and in order
for this to be removed from-the zone of separation either
an up flow of water must be maintained in this zone, or a
; small amount of diluent must be added to the tar sand suf~-
icient to reduce the effective specific gravity of the bitumen
below that of water. The latter procedure is preferred. How-
ever, the amount of diluent added, taken together with a small
.
amount of surfactant which is also added to the water, are
very small in comparsion to the amount of diluent used in
the conventional cold water process. For example, amounts
of diluent (kerosene) between 10% and 100% of the bitumen
content of the tar sand may be suitable for my process(depend-
ing on the clay content of the tar sand); by contrast, previous
cold water processes have used up to about 6 times as much
kerosene as bitumen content. Also, no alkali i5 required, such
a3 tends to cause clay to remain in suspension in the water~
Since the water is not being heated, and since no significant
amount of chemicals are being injected into the water, an
; amount of water giving the best separating conditions can be
used without greatly detracting from the economics of the
process.
In accordance therefore with one as~ectof my invention,
a method for the separation of bitumen fromttar sand comprises
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the steps of:-
mixing the tar sands with water to make a slurry,
agitating and diluting this slurry with additional water
to Form a pulp having a water content at least equal to the
tar sand weight and having a temperature in the range o~E
about 35 to 120F,
Moving the pulp primarily horizontally within a sep-
arating zone at a controlled speed which is low enough to
allow gravity settling of bitumen free sand particles (except
fines) within said zone to form a substantially static sand
bed in contact with the horizontally moving pulp, the speed
being high enough, having regard to any upwards flow of back
wash water, to prevent permanent settling of bitumen coated
sand particles,
withdrawing sand from the bottom of the separating zone
- at a rate suitable for maintaining the bed of sand within
the zone so that bitumen coated sand particles can be freed
from bitumen by tumbling along the upper surface of the bed,
:~ removing water and bitumen from an upper portion of the
separating zone, and
separating a bitumen froth from the water.
The water, after the removal of bitumen, contains fines
i.e. fine sand and clay particles,although since the water
is non-alkali the clay does not form a gel and it is possible
to remove the clay and fine sand from the water and return
this Water to the separatlng zone. ~lso~ the ~ines are pre~
ferably mined with the sand. In one arrangement~ the ~'ines
conta~ning water 1~ recycled to the ~ottom o~ the sand bed and
pumped up through the sand bed so that the sand filters out the
flnes which are eventually disposed of with the sand. This pro-
cedure give~ an upwards flow of water in the separating zone and
helps to float ~he bitumen paxticles to the top of the zone9
~ However, thi~ procedure has some drawbacks, ana I now
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prefer to pass the fines containing water to a settling tank from
which substantially fines free water can be withdrawn for use
in forming the initial diluted slurry of tar sands, and from
which a sludge containing the fines, with some water, can be
removed and mixed with the clean sand.
For this purpose, the sludge can he injected into the sand
bed so that the fines are ~iltered ~rom the water by the bed.
However, the introduction of the clay particles into the
sand at this stage may cause some problems in removing the
sand by a conveyor, and for this reason I ~ay prefer to mix
the sludge with the sand outside of the sand bed while this
is being conveyed to a disposal point.
The separating zone is preferably a vertically
elongated annular space, the pulp being moved around such
space and the sand bed forming an annulus in the bottom of
the space. Moving the pulp around an annulus in this way
insures that all particles are properly treated in the
separating zone no matter how low their settling rate may be.
The pulp- is caused to flow around the space at a speed low
enough to allow settling of bi-tumen free sand particles at
the bottom of the space, and also low enough that centrifugal
forces do not determine the settling pattern of the sand.
The annular space has a radial width which is less, and pre- ¦
erably considerably less, than its inner radius, being
pr~ferably less than 1/2 the inner radius, and in a preerred
arrangement about 1/3, tKe inner~radius~ of the annular~ ~~
space. ~his ensures that the velocity of the phlp~around
the annular space is substant:ially constant, i.e. varies by
less than say 25~ ~in the preferred embodiment about 20%),
from the inner to the outer wall of the annular space.
The speed of the pulp flowing in the separating zone
is preferably between 100 and 200 f.p.m.~ and where this is
an annular space the rotational speed is less than 50 r.p.m.
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to avoid significant centrifugal forces. A preferred speed
for the pulp close to the sand bed (i.e. say 1 inch above
the sand bed) is preferably of the order of 125 f.p.m., and
at least between 100 and 140 f.p.m. The pulp is caused to
flow around the annular space hy Yanes ~hich are spaced
above the sand bed, the velocity of the ~anes being higher
than the velocity of the pulp close to the sand bed, but
this velocity still being less than 2~0 f.p.m. and preferably
less than 140 f.p.m. A generally lamina flow is achieved
around the annular space, although of course with some
eddies being formed close to the sand bed and close to the
inner and outer walls of the annulus.
The reference above to the speed of flow, and the
fact that the velocity is insufficient to allow centrifugal
force to determine the settling pattern of the sand, should
- indicate that the process which I use is quite different
from known centrifugal separation processes. So far as I
am aware! centrifugal separ~tion has not been used for inltial
~;~ separation of sand and bitumen fromttar sands, although-
centrifugal separation has been used to reduce the mineral
and water content of a diluted oil froth which is the product
of an initial separation process. For example, as described in
U.S. Patent 3,893,907 to Canevari, a conventional hot water
type of process is used to separate a large portion of sand
from a tar sand and water mixture, and a froth of water,
non separated solids, and oil is then d:iluted and heated and
passed i.nto first a low speed centrifuye, and then a high
speed centri~uge.
Basic differences between my process and that o~E
Canevari, or like processes, should be evident Exom the
above. Thus, my separation process is concerned with
separating a slurry of tar sands and water which is passed
directly from the agitating step into the annular separation
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zone, without previous processing as suggested by Canevari. Per-
haps more important however is the basic difference bet~een the
relatively slow speed operation o~ my separation zone, and a
centrifugal separation. A centrifugal separation woula cause
heavier particles such as sand to be flung outwardly towards
the wall of a vessel, and if such a vessel were to be such as to
allow a sand bed to settle therein then such sand will settle
preferentially near the outside wall of the vessel. In my process,
by contrast, the sand settles preferentially near the inner wall
of the annulus since the speed of movement of the sand is less
!
at the inside wall than at the outside, and the rotational speed
is so slow that centriugal forces do not counteract this tend-
ency.
Further concerning prior art, I am aware of Canadian
Patent No. 883,974 to Cymbalisty, which shows a separator for
-~ use in the hot water tar sands separation processO ~his contains
rotating blades which agitate the tar sand slurry and cause
separation in a manner which may be similar to that of my agit-
ation step. However, the sand ~ed which foxms in this separator
is not in contact with any horizontally flowing stream of water
carrying the comminuted slurry, but is separated fro~ the agit-
ation zone by a series of baffles which would prevent any horiz-
ontal ~low over the sand bed. Based on my expériments with vert-
ical separation of water, sand and bitumen, the use of this
separator, in the cold water conditions of my process, would
., I
not result in clean sand since lumps of slurry and bitumen coated
sand paxticles would be entrained b~ the falling sand and would
in effect settle on the sand bed.
The horizontal movement pro~ided in my separation zone
3Q inhibits such entrainment by ensuring that sand and bitumen
particles only meet in a glancing manner~ and the horlzontal
movement, also inhibits bitumen particles from becoming adhered
~o sand particles.
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I am also aware of the separator construction used by
Great Canadian Oil Sands ~imited, for example as shown in
Canadian Patent 882,667, in which a circular sand bed in the
bottom of the hot water separator is slowly stirred by a rake.
This may cause some remo~al o~ ~itu~en c~ated sand particles which
have set-tled on the sand bed, although its primary purpose is to
feed the sand to the central sand outlet. However, this general
disturbance of the sand bed is not an efficient way of removing
settled bitumen coated particles. The speed of movement of the
sand rake is kept very low since otherwise power requirements
would be high. Also, the sand rake cannot cause the fluid above
the sand bed to move at a suitable controlled speecl all around
1~ the sand bed and at the radially inner portions thereof.
- My invention also comprises apparatu~ principally in-
tended for the sepa~ation of biturnen from tar sands but which
may have other applications in separating a product from a sand
product mixture, as for example in the separation of potash from
-~ sand and clay particles. The apparatus, comprises:-
a vessel having a top inlet for receiving a fluid
pulp of sand/product mixture and water, a top outlet for water
and product, and a bottom outlet for sand,
said vessel having an inner and outèr:-wall defining
therebetween a vertically elongated annular space, said space
including a sand settling zone having a radial width consider-
; ably less than the inner radius thereof, and :Lying below said
top inlet and outlet and above said bottom outlet and cornrnun-
icating with all o~ said inlets and outlets and being such that
sand can ~low by yravity from said settliny z~ne -through said
bottomoutlet,
a rotor carrying vanes movable around said annular
space above said settling zone for causing movement of the pulp
around said annular space without substantial disturbance of
sand settled in said zone, and
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means (preferably conveyor means) capable of removing
settled sand at a controlled speed from the bottom outlet at such
a rate that a sand surface can be maintained within the settling
zone of the annular space.
Again, such apparatus is clearl~ distinguished
from centri~gal type separators, particularly since such
separators rely on centri~ugal forces for removlny the
sand from the vessel, rather than allowing the sand to ~orm
a sand bed therein and being provided with conveyor means
for removing this sand.
The apparatus also preferably includes agitating
means for agitating the products, sand and water mixture
before this passes into the upper end of the annular space,
and the agitating means may include co-operating vanes
~ operating in an upper annular space which communicates at
- itslower end with the vertically elongated annular space,
- the co-operating vanes including vanes carried by the rotor.
A feature of apparatus in accordance with the
; invention is that this is relatively compact compared to
presently used apparatus for tar sand separation, and I
contemplate that a portable form of such apparatus may be
built. In this case, the separating process may be operated
near the sand digging face, avoiding problems with trans-
porting the tar sand over a long distance to the separatiny
plant, and transporting the clean sand back to the digging
face.
Other features and advantages oE this invention
will appear from the following clescrption o~ the attached
drawings wherein:
Fig. 1 is a sectional~elevation of an extraction
apparatus embodying one form of the~`invention,
Fig. 2 is a schematic view of a modified and larger
plant embodying the invention,
1~ 7
;Fig. 3 is a partly~fiectioned elevation view of a
separator used in the Fig. 2 plant,
Fig. 4 is a view on lines 4-4 of ~ig. 3, showing
part of sand conveying means, and
Fig. 5 is a diagrammatic view of a ~odified form
of separator.
With specific reference firs-t to Figure 1 of the
drawings, the apparatus consists generally of a receptacle 1
for receiving the tar sand mixture from the excavator, a
; 10 mechanical mixer 2 having rotating paddles 26 which functions
to break up the lumps of tar sand to a more homogeneous
mixture, a source of water 3 which is fed into the tar sand
mixture and is mechanically mixed wi-th tar sand to form ~
a slurry; a hopper 4 into which the tar sand-water slurry
is deposited and a revolving wheel 5 which removes from the
top of the slurry any deposits of oil which may have risen
to the surface of the slurry in the trough! 4.A trough 6 is
disposed against the outside surface of the wheel 5 to re~ove ¦
any of the oil which as been deposited on the outside surface I i
of the rotating wheel. A ~inned conveyor ~elt 7 serves to
remove the tar sand mixture from the bo~tom of the hopper 4
so as to permit it to slide under gravity along a chute 8
into the top of the separator 9.
This separator 9 is composed of a power shaft 10
on which is fixed a rotor 11 which has conically shaped upper
and lower portions 14 and 15 which converge respectively upwards
and downwards from a common central plane where both portions
have the same diameter, to the upper and lower ends of the
'rotor where the diameters are the same as that o~ shaft 10.
30 T~le separator 9 includes an outer casing 12 which serves to
contain the tar sand slurry within the casing and also to
guide the movement of the various materials and water in a
manner hereinafter described. The lower part of casing 12 is
generally parallel to the outer surface o the lower portion
of the rotor and forms there~th a ~ertically elongated,
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downwardly converging annular space having a radial width
considerably less than its inner radius.
Contained within the outer casing 12 is an inner
casing 13 which encircles a portion of the shaft lO as well
as the upper portion 14 of the rotor, forming therewith a
downwards diverging annular space. This inner casing 13
se~JeSto guide the slurry downwardly onto the outer sur~ace
of the upper rotor portion 14 and to guide the bitumen-water
mixture as it leaves the separator as hereinafter described.
Attached to the outer surface of the upper portion
14 of the rotor ll is a series of vanes 19 which co-operate
with stationary vanes 13a on inner casing 13 to agitate and
~ break up lumps of the slurry as it moves downwardly along
-- ~ ~ the outside surface of the rotor this process forming a
substantiallyhmgeneous pulp. Attached to the lower inclined
surface 15 of the rotor ll is a second series of vanes 16
which extend Yertically do~n the upper part (about half way~
of su~face 15 and ~hich cause the slurry to move in a rotation-
al direction around the annular space between surface 15 and
the casing 12.
Attached to the central shaft lO below the bottom
edge of the rotor 11 is a further inner casing 17 which
functions to direct a downflowing sand-wate~ mixture away
... . .
;~ grom the base of the shaft 10 ~na t~-p~eyent t~`~ sand fr~
l entering the exik end of a water pump 18.
; Attached to the lower erd of the casing 12 adjacent
to the left side of the casing is a sand auger mechanism
20 which is comprised o an outer casing 21 and a powered
spiral auger 22. At the top side edge of the auger casing
' 30 21 there is an exit chute 23 whichsserves to carry cleaned
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sand out and away from the auger casing 21. The auger 22
may be powered through a variable speed drive 24 by means of
the power source for the separator 11 (not shown) which may
be a conventional electric motor attached by means of a
drive mechanism to the separator shaft 10.
Adjacent to the right hand side of the separator
9 is a trough 30 which is attached at its one side to the
top of the outer casing 12 and at its other side to a water
return conduit 31.
Disposed within the trough is an endless conveyor
32 which functions to carry agglomerated particles of bitumen
out of the trough 30 to be collected in collecting trough
33, while permitting water, fine particles of sand and clay
to remain in trough 30. Also disposed within the trough 30
is a rotating oil collector wheel 34 which serves to skim
any oil floating on the surface of the water mixture contained
in trough 30 and to deposit it in a collecting trough 35
where it can be carried away to a holding or collecting tank
(not shownl.
The apparatus of Figure 1 operates in the following
manner. The tar sand mixture is received from the excavators
and is deposited in the infeed receptacle 1. The mixture
may have a temperature of approximately 40-~0F so that
except in winter, no heat input is necessary. If waste heat
is available however, this can be used and wil:L increase t.he
eficiency of the operation. During winter operations, it
may be necessary to enclose the gear mechanism which lelivers
the tar sand mixture from the excavatGr to the separator
apparatus. The tar sand mixture which will contain a small
amount of moisture is mechanically mi~ed by the rotating
paddles 26 of the mixer 2 until the lumps of sand and tar
have been broken down. Water is introduced to the mixture
- 14 -
.~ . , -
through the conduit 3 at a rat~ of approximately 30 lbs. water
for each 100 pounds of tar sand mixture. Because of the
different specific gravities of water and tar sand~ this
should result in a mixture of tar sand and water having a
1:1 ratio by volume. If the temperature of the tar sand
mixture is not too far below 40F. then the water need not
be heated but can be drawn directly from a local source such
as a river or lake. As the water and tar sand mixture pro-
ceedsthrough the mechanical mixer 2, the action of the
paddles 26 forms a slurry. Because of the sloping bottom
wall on the mixer 2 the slurry moves in the direction of
the trough 4 where it flows into the trough and the heavier
particulate material settles to the bottom. The tar sand
mixture normally contains small amounts of free oil and this
; oil-will float to the surface of the slurry where it is
moved,by a rotatiny drum 5 and carried away from the trough
6 to be stored in~an appropriate receptacle. The ,lighter
-' portion of the slurry flows out of trough 4 through conduit
, 8 into the top of the separator 9. The heavier parts of
the slurry including the sand and tar particles are drawn
out of the bottom of the trough 4 by means of the endless
conveyor 7 and these heavier parts also travel down through
the conduit 8 into the top of separator 9. The slurry collects
within the upper walls of the inner casing 13, flows downwardly
onto the top surface 14 of the separat,or rotor 11 where, through
the, action of gravity, the slurry flows outwardly towards the
inside surface of the outer casing 12. rrhe rotation of ~he vanes
13a with rotor 11 c]ose ;to the stationary vanes 19 causes agit-
akion of the slurry and any remaining lumps of tar sand are broken
up so that a homogeneous slurry passes into the lower part of
the separator surrounding surface 15, where it mixes wi-th up-
wardly flowing wash water to form a pulp. The agitation process
also separates a large part of the bi-t~nen fro~l the sand part-
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ticles, so that this contalns clean sand particles and
bitumen nodules along with some bitumen coated sand.
The sand particles tend to move downwardly against
the slight movement of the wash water which is being pumped
upwardly through the separator by the pump 18 as indicated
by the flow lines in Figure 1. At an operating temperature
; of 40-60F the bitumen tends to collect into nodules when
separated from the sand particles within the separator. At
the temperature range of 40-60F the bitume~ has a specific
gravity which is slightly heavier than water, generally in
the range of about 1.002 to 1.02. It is not sufficiently
heavy to move quickly downward with the sand particles
against the slight upward flow of the wash water through
the separator, with the result that the bitumen particles
~; move upwardly with the flow of water and out of the separator
and into the trough 30. As the flow of wash water upwardly
through the separator is not sufficiently fast to carry away
the sand particles, they settle downwardly through the
wash water and deposit themselves in the lower part of the
separator 9 between the outer casing 12 and the lower part
15 of the rotor 11. It has been observed in laboratory
tests that the sand particles are held in suspension by the
rotating vanes 16 of the separatorrotOr 11 until they arrive
at a point just below the~bottom edge of said vanes.
This point or level in the annulus formed between
the inner rotor 11 and the casing 12 I call the critical
zone and a bed 37 of cleaned sand forrns in this zone, with
a fairly discrete surEace 38. It has unique properties due
to the conical design and rotational speed of the vanes on
the rotor 11. The separation of bitumen from sand particles
occurs due to abrasion between the bitumen coated sand part-
icles, which mostly vccurs in the slurry forming and agitation
stage, but also occurs close to the sand bed where particles
are rolled along until they release their bit~nen. The sand
I
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bed surface occurs at a point where the velocity of movement
around the annulus is not sufficient to keep clean sand part-
icles in suspension, the velocity of the movement of course
decreasing from the lower ends of vanes 16, by reason of
fluid friction on the sand bed and sidewall and by reason of
.
the decreasing radius of the annular separation zone. Only
substantially clean sand particles will settle in the
critical settling zone since all other material present
in the cell has a lower specific gravity and will therefore
either be kept in fluid suspension or will roll along
the surface 38 of the sand bed until substantially all
of the lighter material is abraded from the sand surface.
Then the resulting clean sand will immediately settle to
the bottom of the settling zone lsurface 38 of the sand plug
37).
. . :
The flow rate o~ water recycled into the bottom of
separator should be slower than the rate at which the sand
would be fluidized. The chief reason for the counter flow
is to provide a cleansing action on the water for removal
of some of the suspended solids, such as clay, by filtration
through the sand. The speed of rotation of vanes on cone 11
. and speed of water counter flow must be too low for clean
sand to stay in suspension. At the critical interface point
38 the speed of rotation should be too high for bitumen
; to settle. A speed of about 1~5 .~.m. has been found suit-
able; thi5 speed, given the diameter of the separator does
not cause any signiicant centrifugal separation o the sand.
The accumulated cleaned sand 37 at the bottom of
the separator flows under gravity and by pressure from the
incoming material downwardly towards the base of the auger
. .
mechanism 15 where it is carried upwardly ~nd out of the
auger mechanism through the discharge trough 23
~ 17 ~
!
6~
The bitumen nodules, which have some sand particles
entrapped therein, are carried upwardly through the separator
and out of the top of the separator into the trough 30, where
the bitumen nodules, being, in the absence of solvent, heavier
than the water, sink towards the bottom of the trough 30
where they come into contact with the surface of
the conveyor belt 32. The conveyor belt 32 carries the
bitumen nodules out of the trough 30 and into collecting trough
33 where they can be removed by anyconventional means such
.: 10 as tanker trucks or when mixed with petroleum solvent, by
pipeline to a central processing plant fo.r secondary process-
ing. Any free oil remaining in the water is removed from
the surface of the water in the trough 30 by means of rotating
drum 34 and the collecting trough 35. This oil as well as
the oil collected in the trough 6 may be stored in sultable
; receptacles or may be mixed back in with the bitumen nodules
~: in the trough 33.
~ ater ,flows out of the trough 30 and into the
conduit 31 where it is returned to the inlet end of the pump
18 and is pumped under pressure through the sand 37 which
has collected in the area adjacent the bottom of the rotor 11
.~ and hence upwardly along the annular space between the rotor
11 and the outer casing 12. The sand parti~les which ha~e
collected in the lower portion of the separator act as a
filtration bed to remove from the returnlng wash water a
portion of the silt and clay particles which were carried
, ! upwardly with the bitumen nodules by the flow of the water
: through the separator. q'he fine clay and silt partic].es which
are entrapped by the coarser sand particles are carried out
of the separator by the auger mechanism 2Q. The am~unt oE
water recirculated is controlled, as by admission of make-up
water, so that the total amount of water in the pulp being
separated within the annular separation zone is between 1 and
3 times, andpreferably 2 to 2 '/2 times, the weight of tar
sand.
; It is important that the peripheral speed of the
rotor 11 rotating the vanes 16 and 19 be correlated with
; the density and temperature of the slurry as well as the
rate of flow upwardly of the wash water in order to ensure
that the sand particles settle out of the slurry against
the flow of the water while the bitumen nodules are carried
upwardly and out of the separator. This can be controlled
easily by visual observation of the level 38 through a
window, or by other conventional means.
As the water level in the auger mechanism 20 will
always be below the opening into the chute 23, the cleaned
'';A sand which is removed from the auger mechanism by the chute
23 will ha~e with it only that portion of the water which
is entrapped on the sand particles, as well as clay returned
; thereto by the recirculating water.
If apparatus in accordance with the invention is
made portable, this will permit the removal of most or all
~ sand from the bitumen at the mine site by a cold washing
- process. This would make it possible to dispense with the
need for the extremely expensive conveyor belt for carrying
the sand to a distant treatment plant. At its best this
5y~,tem may provide a pumpable oily liquid whlch may be sent
by pipeline to the treatment plant. In the alternative,
this invention may be used in a concentration step for removal
of 60 to ~0 per cent of the sand at the mine site, with
-the remaining sand being present in a pumpable sand - oil -
water mixture~ The pipelines may be buried under the clean
sand behind the mobile mine site extraction apparatus.
Only a supply of cold water is needed at the mine
¦ site, if the method is used as a concentration method.
, '
, _ 1 9 _
~' .
z~
If the method is used for total removal of sand
at the mine site then some solvent will also be used. Any
convenient solvent may be employed. The higher flash point
materials are sa~er to use, but they generally exhibit lower
solvency. Low flash point material such as naphtha may be
used. This is very efficient, and leaves very little
residue in the cleaned sand. Howe~er r it involves a high
I fire hazard and evaporation losses. Kerosene or gas oil may
- also be used. In particular kerosene involves a relatively
low fire hazard, and very low evaporation loss. It is not
quite as good a solvent for bitumen but it is found to be
acceptable. More heat is required to drive it off from
the bitumen for recovery and recycling. ~ith the process
described, using substantial flow of back wash water lO to 20
I per cent of solvent based on bitumen content will desirably
be added, as the small amount of solvent greatly lowers the
viscosity of thebitumen, and renders it more easily separable
from the sand and later from the water by reducing the density
of bitumen and making it buoyant.
iC If a countercurrent back wash is provided it will
remove some residual solvent from the sand.
Example I
In apparatus similar to that of Fig. l, 100 l~s.
of tar sand material was mixed with 30 lbs of water, and
mechanically mixed to produce the desired constit:uency of
the slurry. The lO0 lbs of raw material contained about
15 pounds oE bitumen and 85 pounds of sand plus small amounts
of water and clay. Seventy pounds of clean sand collected
at the bottom of the separator together with approximately
25 pounds of water. A total of 35 pounds of material com-
prising 15 pounds of bitumen, 15 pounds of sand and 5 pounds
of wa-ter and a small amount of oil was carried upwardly out
of the separator and into the holding tank. In addition to
.
~ - 20 -
37
the 5 pounds of water carried with the bitumen there was
125 pounds of water which is composed of 25 pounds of water
remaining from the 130 pounds of slurry and 100 pounds of
wash water which was passed up through the cleaned sand
deposited in the bottom of the separator.
31 lbs of Raw material (bitumen sand) was mixed
for approximately 10 minutes with Naptha in the ratio of
31 X 16 X 0.2 (Naphtha) 0.992 per 31 lbs raw material.
'' 100
Water was added in the proportion of 31 X 16 X 0 4 = 1.984
This resulted in a slurry of raw material = 31.000 lb
Naphtha = 0.992 lb
Water = 1.98~ lb
Total weight 33.976 lb
: ~.
This material was fed into a separator in accordance
with the invention and operated for 15 min. Therefore,
Extraction rate of machine tested = 31.0 X 4 = 124 lbs per
., I
hour. Therefore, assume bi~umen content = 16% oE dry weight,
then the bitumen extraction rate was 31 X 16 X 4
100 = 19.84 lbs
per hour or 476.6 lbs per day. The annular sand settling
area of this machine used in this test had inner and outer
~' diameters of 7" and 9" respectively.
Batch # l-A Sample Run
~._
:: ANALYS.IS OF RESIDUE MATE'RIAL ~BITUMEN) REMAINING IN T.AILINGS
a) A sample of (tailings) was taken from the tailings oE a
31 lb. run of raw material. A quantity of this material was
dried over-niyht at 200F
Weight of Flask = 98.1 g
Dry Tailings - 200.0 g
298.1 g
b) ~he 200.0 g dry wt. sample was washed wi~h na~hthæ
,in a total of 5 washes (the 5th wash being completely trans-
- 21 -
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parent & therefore considered clean). This sample was then
thoroughly dried by evaporation at 300F and re-weighed.
TOTAL = 297. 8 g T~e~e~oxe, M~terial ~eight = 200 n O g
F~ASK = 98.1 g Minus washed Material weight c 199 . 7 g
DRY TAILINGS = 199.7 g Equals soluble conteIlt = O . 3 g
Known bitumen content of this sand batch in i~s' original
(Pre-Processed State) was 16.4% Wgt.
Therefore, original Bitumen content associated with 200 g of
sand was:
10Original Total Weight (200 X 100) X 16.4 = 39.234
( 83. 6
Therefore, % of material not recovered from Sand = ( 0. 3 ) X
~: ( 39.234 )
100 5 . 7646%
:,
Therefore, if loss is .7646% ~in tailings)
then recovery in water & solvent is - (100 - .7646) = 99. 2345%
Note:
This figure of .765% does not include any loss that
may occur due to suspended bitumen in the clay-water filtration.
~.
The above description relates to a laboratory scale
apparatus. A larger apparatus has now been built, and is
described with reference to Figures 2, 3 and 4. One major
difference of the new apparatus is that, instead of water
from the separator being recycled through the sand bed, the
water passes to a settling tank from which relatively clean
water is passed to the incoming slurry as this is being fed
to the separator. A sludge of clay, and fine sand, with
water, is withdrawn from the settling tank and mixed with
the clean sand~ Only a small amount of xelatively clean back
wash water is used, 80 that there is little upwards ~low of
water in the separator. This makes it necessary to use an
amount of solvent sufficient to reduce the effective specific
gravity of bitumen to less than 1 ha~lng regard to any solids
content.
~,,
-22-
~ ~ .
: ;,
Referring to the layout of the new plant shown in
Figure 2, the main items are:-
a preliminary tar sands treatment apparatus indicatedat 100,
a separator vessel indicated at 102,
,apparatus for separating bitumen from water, indicated
at 104,
a settling tank for sepaxating water from clay and
fines, indicated at 106, and
a recycled water treatment apparatus indicated at 108.
Tar sand, as mined, is passed through a star wheel
feeding device 110 which breaks up any large agglomerates of
the tar sand, and feeds this onto a belt conveyor 111. The
;~ sand falls from the belt conveyor into a chain flail device
112 which breaks up lumps of the tar sand r the tar sand then
passing onto chute 113 which lea~s to entry end of a slurry
~:, forming feed mill 114. This mill rota~es about a horizontal
axis and has an internal helical flight so that it operates
in manner similar to an Archimedes' screw. A pipe 115 lea~s
to a spray device arranged to spray water onto the tar sand
within the chain flail device 112, to give preliminary wetting
of the clay therein. A further pipe 117, fed with diluent
through a diluent metering pump 120 from tank 121, leads to a
further spray device within the mill wh.ich sprays diluent on
the tar sand suff;.cient, when absorbed by the b.itumen, to
reduce the effective dens,i.ty of the bitumen (at room temp-
erature) to helow that of water so that the bitumen is buoy-
ant in the separation process. The tar sand slurry leaving
', the mill enters a rotating, selfcleaning screen 1~4, which is
provided with a supply of wash water from tank. 126 via spray
device 127, The screen 124 removes lumps of-clay, or stones,
from the tar sand slurry, these l~aving throu~3h a chute 130.
The removal of clay lu~ps at this stage is very useful since
- 23 -
,
L8~
this clay does not have to be separated at a later stage from
the water. A further screen (not shown~ may be provided to
remove over-size agglomerates of tar sand and return these to
the inlet end of the mill.
The tar sands which have passed through the screen
wash, and mixed with the water from device 1`27, enter the
top of the separator 102 which is shown in detail in Figure
3 of the drawings.
The separator vessel has an outer casing 150, of gen-
erally downwardly converging conical form, supported on legs 151v
The casing however incl~ldes an upper portion 150a which
diverges downwardly, a short cylindrical section 150b next
below this, an upper downwardly converging section 150c having
a window 152, and a lower section 150d which converges down-
wardly more sharply than section 150c. Within the vessel
there is fixed inner casing 153, which also converges down-
,, ~ .
~- wardly in two stages generally matching the converging
~; sections of the outer casing. The lower part of the inner
r' casing is rig~dly connected to the outer casing by a series
of circumferentially spaced supports 155, which are tubular
in cross-section and are also elongated in the vertical
, ., ~
; direction so as not to unduly inhibit the flow of sand
around them. The inner casing includes an upwardly converging
; upper section 153a, joined to the downwardly converging
; sections by cylindrical section 153b. The inner and outer
casings thus define between them, beginning at the top of
; the vessel, a downwardly diverging annular space, a cylindrical
Z annular space, a vertically elongated separation zone 157
which converges downwardly both in respect of its inner and
outer radius and respect of its radial width, and below this
a sand bed space lS8 between the lower casing sections, the
diameter of which aiminishes downwardly, but the radial
width o~ which increases in the downwards direction. The
!
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',~
~, ::^' , . . :
, .
~ ( 7
upper end of the separation space 157 has an outer diameter
of about 45 inches and an inner diameter of about 33 inches
so that in this annular space as a whole the radial width
is about 1/3 of the inner radius, and certainly less than
1/2 of the inner radius.
In this embodiment, the rotor is not attached to
the inner walls of the separator vessel, but is in the form
of a frusto-conical plate 160 which extends between the upper
portions of the inner casing 150a and 153a, being carried
via a short cylindrical section 160a and connecting members
160b, by an annular plate 162. This annular plate has an
I outer flat portion which is gripped between rollers 164 and
-~ 165, the lower roller 164 being driven by a motor 166 to
rotate the ring 162 and with it the rotor. The plate 160
~ carries a series oi radial vanes 168, extending from the
.- underside of plate }60 and having ir~egular lower edges which
are complementary to and spaced a~o.ut l/4'! a~ave-the upper edges
of radial vanes 169 fixed to inner casing portion. 153a. The
slur.ry is arranged to be fed in through tube 170 between the
inner casing portion 153a and the rotor 160, so that the 1,
vanes 168 and 169 break up the slurry as this passes aown
the annular space between the rotor and the inner casing,
an~ agltate tne slurry so t~at lt rorms a pulp wl ~n the wate~.-
The rotor 160 also carries a series o~ vanes 175
which are of vertically elongated form ancl wh:ich extend
down into the top of the separation zone 157. These are
arranged to cawse a steady rotary movement of the tar sand
: and water pulp around the zone 157. The speed of the motor
166 can be varied to give the rotor speeds between 10 and 14
r.p.m. Taking 10 feet as the c.ircumference of the top of
zone 157~ the vanes 175 can have speeds between 100 and 140
f.p.m; the preferred speed ~eing around 125 to 130 f.p.m.
~ .
:
~ - 25 -
At the lower end of the ~u-ker casing is proYided
a generally cylindrical sump area 18Q whic~ hold~ the lower
end of the sand bed. A series of fixed vanes 181 extend
into this sump area, also shown in ~igure 4. Spaced from
the inner edges of the vanes 181 is a sand scoop rotor 184,
which is attached to the lower end of an auger 185. The auger
185 extends axially upwardly through the separator vessel,
within a tube 186. A lower port~on of the tube 186~ which
communicates with the annular space between the lower conical
portions of the inner and outer casings, has a series of
radial vanes 188. The sand scoop rotor 184 thus operates
in a portion of the sand bed which is largely prevented from
; rotation by the vanes 181 and 188, so that the scoop members
; 187 of the rotor are effective to scoop the sand inwar~ly to-
wards the bottom end of the auger. A bottom portion of tube
- 186 extends within rotor 184 and has openings defined by lou~res
- 189 angled to assist the inwards movement of sand as the-rotor
rotates.
A central portion of the auger tube 186, starting
close to ~he lower extremit~ ~ the inner Yes'sel ~ is
surrounded by an outer sludge tube 190, into the upper end
of which sludge can be injected through pipe 191. Ports 193
are provided in the wall of the auger tube 186, to allow
sludge to flow from the sludge tube into the auger tube to
be carried upwardly with sand being transported by the augera
The upper end of the auger tube connects onto a sand disposal
chute 194.
Around the base oE the separation zone 157 there
is provided a series o~ back wash water injection inlets.
These include a saries of small tubes 195 attached to a
back wash water manifold, and a series of baffles 196 which
provide a containment space above the ends of tubes 195 and
ensure reasonably good dispersion of the back wash water into
the sand without channeling.
- 26 -
.
3 ~6~
The separator vessel has a bitumen and water outflow
pipe 198, which extends through the outer upper wall 150a of
the vessel, above the level of the vanes 175. As seen in
Figure 2, this bitumen and water outflow pipe leads to the lower
end of a first plate separator 200, the bitumen and water mixture
flowing up between the parallel plates of the separator to a
reservoir portion 202 where -the bitumen, freed from some of the
fine sand, rises to the top of the water. The upwards flow
disposition of the separator is primarily designed to allow some
fine sand and silt to separate out from the water, and this is
disposed of through the outlet tube 206 to the same disposal
point as the sand.
The bitumen layer on the top of reservoir 202 is moved
- by elongated rotating paddle devices 210 into a second reservoix
212, where some further fine materials separate and are removed
through a sump valve 214 to join line 206. The bitumen layer on
the top of reservoir 212 is picked up by a mechanical scooping
device 215 and passed -to an outlet tube 216 for the diluted
bitumen. The bitumen is then sent for further processing, for
example by centrifuging and fractional distillation.
Wa-ter flows out of reservoir 20~ into a tank 220,
barrier 219 preventing the surface bitumen from also f:Lowing out.
The splashing of water into tank 220 releases some more bitumen
which float~ to the top o~ this tank and is pumped into pipe 222.
Water passes rom the bottom of tank 220 into tan]c 224, from where
it i8 pumped by pumps 225 and 225A into pipes 222, passing along
from tank 220 into ~he top o~ a second plate separator 226. The
bitumen within pipes 222 does not mix with the water but remains
in the top of separator 226 where it mixes with further bitumen
removed from the water by this separator which is orientated for
- 27 -
:
.,.
, .
.
bitumen separation. This bitumen leaves the top of the
second plate separator and is returned via line 227 to the
reservoir 202. Also, a small amount of fines can be removed
from the bottom sump 229 of this second plate separator. The
water leaving this separator however still contains a certain
amount of fine sand and silt and considerable quantities of
clav particles, and these ~ass via a line 230, firstly to the
central column, and then to the rotating boom assembly of the
settling tank 106. This settling tank is circular in plan view
and the rotating, radial, boom assemblv is designed to allow
the water and clay suspension to enter the top of the settling
tank, via the rotating boom, in a way which creates minimum
disturbance of the ~urface of the settling tank. Simultaneously,
the rotating boom is arranyed to remove a top layer of the water
lying in the settling tank, ahead of the insertion of the dirty
water, so that the boom is continually scooping up relatively
clean water at its front end and leaving the dirtier water at
its rear end. This settling tank is the su~ject of Canadian
Patent 1,109,002 issued Sepkember 15, 1981, and will therefore
not be further described herein.
The fine sand and clay collects in the sump 2 4a of the
settling tank and is moved ~y a pump 242 to a sludge storage
tank 244 from which it i5 periodically pum~ed bv a further pump
246 ïnto the sludge inlet pipe 191 of the separator for mixïng
with the cleaned sand.
Relativelv clean water picked up by the boom aasemblv
of the setkling tank is passed via line 255 to the recycled water
treatment apparatus 108. This includes three containers, 260,
262 and 264, and the water from the settling tank is
directed into the central container 262. This relatïvely
clean water, but which contains small amounts o fines and
- 28 -
~ ~ .
clay, is recycled by pump 266 through pipe 268 back to the
storage tank 126 which supplies the water for mixing with
the incoming tar sand.
Since some water is continually leaving the system
in the sand and sludge, and in the bitumen froth, there is
a continual need for makeup water which is supplied through
pipe 275, which leads through flow control devices into the
left hand container 260 which contains clean makeup water.
Abranch pipe 276 is connected into pipe 275, and supplies,
via a metering pump 277, small amounts of diluted surfactant
from tank 264. A connection 278 bet~een containers 260 and 262
allows some of the clean water, with the surfactant, to pass
back into the recycled water. ~owever, most of the clean
water in tank 260, and having the surfactant, passes firstly
via pipe 280 and metering pump 282 to the water spray which
initially wets the incoming tar sand. A further amount of
this clean water is passed by injection pump 286 and pipe
287 into the separator vessel via pipe 195, to provide the
back wash water for the sand. It is found that using clean
back wash water for the sand is desirable to avoid this
becoming clogged by fines.
The apparatus as described abo~e is cap`able of
accepting about ofiê metric ton per hour of input tar sand.
In operation, the sand as mined is fed via star
wheel 1l0, which breaks up large ac3g:Lomercltes o the
tar sand, and -this then passes on conveyor 111 into
chain flail 112 where the incoming tar sand is sprayed
by water from pipe 115, the amount of water beiny
just sufficient to wet all the clay in the feed. With- I
out this prewetting, an undesirably large proportion of the
diluent will be absorbed by even quite small amounts of clay
mixed with the sand. The amount of water ~or a gi~en tar
- 2~ ~
.:
6~
sand composition can be found by taking a sample of the tar
sand and soaking this in wa-ter for about 1 minute, and then
lifting the tar sand from the water and determining the amount
of water absorhed. The amount will vary greatly with the clay
content of the tar sand, being generally between 5 and 60% of
the tar sand weight. Where it is inconvenient to pre-test the
tar sand in this way, the pre-wetting water can be added in
several stages, within the mill, and the consistency of the
slurry observed.
The wetted tar sand after passing into the mill 114, is
sprayed with diluent, preferably kerosene, ~ia the pipe 117.
The amount of diluent can be varied quite widely, since only
; a small amount is needed to give the desired reduction in
density of the bitumen 7 but it can be helpful to use larger
quantities in that the bitumen froth produced by the process
contains less entrapped fines and water droplets when a fairly
large amount o~ diluent is used. The diluent can be largel~
recovered in subsequent processing. Generally, an amount of
diluent between 25~ and 100% of diluent per unit weight of
bitumen content of the tar sand is used.
The wetted tar sand with the diluent is tumbled in
mill 114 for 20 minutes, to form a slurry in which the diluent
is properly absorbed. This milling operation, performed with
limited quantities of water and diluent, itself causes bitumen
to break of~ the san~ particles since the hitumen to bitumen
; adhesion is stronger than the bitumen to s~nd adhesion. The
slurry then passes into the screen separator 12~ t ~here it is
sprayed with water from spray device 127~ The chain flail 112
and mill 114 are such as not to break up hard lumps of clay,
so that these lumps can be disposed of along ~i-th stones,by
the screen~ Unbroken aggregates of tar sand can be remo~ed
by a separate screen and returned to the inlet end of the mill.
The mixture of tar sand slurry and water then passes down pipe
":
- 30 -
'
~26~
17 into the separator. The amount of water used at this
stage is usually such as to bring the total water content of
the mixture up to between 2.5 and 3 times ~he weight of tar
sand. This mixture passes, from pipe 17b, into the diverging
annular space within the separator between the inner casing
part 153a and the rotor 160j where it is agitated and commin-
uted by the c~osely spaced relatively moving vanes 168 and 169.
These vanes disperse the tar sand in the water as a pulp, and
in addition cause an abrading action between the tar sand
particles, and a rotational action, which further separates
the bitumen from the tar sand before this passes into the
annular separating zone 157.
On passing into zone 157 the pulp is moved around this
- zone in a steady manner by the vanes 175, and since this zone
is free of internal projections the pulp here loses its tur-
-~ hulance and r~tates as a body within the zone. The speed of
movement is such that any particles with more than a minute
amount of bitumen adhering thereto are kept in suspension, as
are fines. The released bitumen and fines tend to flow upwardly
within the outer annular space surrounded by the outer casing
part 150b, and thence out of the water and bitumen outlet
pipe 198. Tn the lower part of the separation zone a bed of
sand forms which is almost entirely of clean sand. The sand
bed surface can be observed through the window 152, and this
allows the speed of the vanes 175 to be sui-tably adjusted to
ensure that only clean sand settles on the bed, and so that
not too yreat a quantity of sand particles is kept in suspension.
Sand is continually removed from the boktom o the
bed by the com~ined operation of the rotor 184 and the auger
185l the scoops of the rotor acting against fixed vanes 181
to scoop the sand into the bottom o~ the auger which then
carries the sand up through -the tube 186 to the entry point
into the disposal chute 194. Some drainage of the sand occurs
`:
- 31 -
. . .
since the top of shute 194 is above the water level in the cell.
However, there is a constant loss of water from the sysrtem in
the sand which contains about 25% by weight o~ water. Sludge,
i.e~ fine sand and clay mixed with water, and which has previous~
ly passed Ollt of the water outlet pipe 198, is recovered from
the settling tank and is injected down the pipe 191 to pass
through the ports 193 into the sand moving up the auger. In
this way, the sludge can-be removed well mixed with the sand~
and does not pollute the environment to a major extent
The liquid leaving the pipe 198 is about 90~ water,
about 5~ bitumen and solvent mixture, and around 5% fines
(clay and silt)~ Some of the bitumen is combined with the
clay in a colloidal suspension. In the bitumen extraction
apparatus 104, which includes the two plate separators and
the tank 220, substantially all of the free bitumen and
solvent mixture is removed as a ~itumen froth which also
contains some waters and some fines, and which is suitable
.
for further processing by conventional means. The majority
of the water, fines, and the colloidal suspensions pass into
''' . J
the settling -tank, where the fines settle out for removal
; as a sludge, and reinjection into the sand as described.
Fairly clean water is removed from the settling tank, and
passed to the water treatment area 108, from where the water
is recycled largely to the incoming slurry.
As indicated, for back washing of the sand bed,
I now prefer to use substantially c]ean makeup water,
¦ , with some surfactant, which is stored in the tank 260. This
is injected via the pipe 195 into the sand bed in a pulsed
manner to avoid charmelling of the water through the sand
bed. The primary purpose of the back wash water is to
remo~e from the sand the few particles of bltumen which
are entrained therein, and also to remove the finest particles
which otherwise hinder drainage of water from the sand.
It ~ill be appreciated that many changes may be
~ 3~ -
~6~
made in this process within the scope of the invention.
Thus, while it is an economic advantage of the
process that it can be used with room temperature, unheated
water, there are advantages to using heated water if a
suitable supply of cheap heat is available. Also, the
proportions of the incoming mixture which can be used, as
to proportions of water to tar sand, and diluen~ to tar sand,
are widely variable, depending on economic ~ircumstances. t
Thus, using plenty of diluent is desirable in producing a
1~ froth which does not trap much fines and water, but on the
other hand an acceptable froth can be produced using only a
small amount of diluent should this be better for the overall
. economics of the process~ Also, it is quite possible to
,- i
use an amount of water more than 3 times the total weight
of tar sands.
Figure 5 shows a further embodiment of separator,
and illustrates that the step of separating bitumen particles
: from sand particles to give a clean sand bed can be performed.
separately from the agitating and comminuting step. The
upper part of the separator is connected to any convenient
very high turbulance pulp feed device, from which pulp
enters through inlet 370. The pulp is rotated around
annular space 375 by vanes 376 on rotor 377 which, as in
the first embodiment, also forms the inner wall of the
allnular space.
Auger 350 is fixed to pipe 355 which may be
stationary but is prefera~ly rotatable in a directi.on
opposite to the rotor direction to allow for variation of
sand removal independent of rotor speed. The auger 350
rotates within rotor support casing 357 provided with wing
SCOOp5 358. Back wash water enters the pipe 355 through lnlet
373 and leaYes the pipe through ports 360, trickling between
- 33 -
cup 361 and inverted fitted cap 362. Xtthen passes upwardly
past flexible seal 363 and upward into settling zone 354.
- .
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, I - 34 -
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